1. Field of the Invention
The present invention relates to an apparatus for supplying fuel in a fuel tank to an engine through a diaphragm-type carburetor.
2. Description of the Prior Art
An engine used, for example, in an engine-driven mowing machine is unstable in its attitude during operation. This results in an unstable attitude of a carburetor used to supply fuel to such an engine. In order to achieve stable fuel supply independent of the attitude of the carburetor, a diaphragm chamber has generally been provided in the carburetor. The diaphragm chamber includes a diaphragm through which the diaphragm chamber is in contact with the atmospheric pressure, a fuel inlet in which a fuel valve is provided, and a fuel outlet which communicates with an intake pipe of the engine through a nozzle. When the intake pressure of the engine is reduced, the diaphragm is deflected to open the fuel valve, permitting fuel introduction into the diaphragm chamber. When such introduction of fuel into the diaphragm chamber increases the pressure therein to a predetermined level, deflection of the diaphragm is relieved, so that the fuel valve is closed. Repetition of this operation permits the diaphragm chamber to normally store therein fuel of a constant volume at a constant pressure. This assures stable fuel supply independent of the attitude of the carburetor.
In order to supply fuel to the diaphragm chamber, a fuel pump is generally employed which is driven by pulsation pressure caused by rotation of the engine.
In general, when an engine with a diaphragm-type carburetor has been kept out of use for a long time, the diaphragm chamber and a pipe connecting between the diaphragm chamber and the fuel tank become empty.
Once the diaphragm chamber and the pipe between the diaphragm chamber and the fuel tank have become empty, it takes a rather long time after starting of the fuel pump to refill the diaphragm chamber with fuel, resulting in substantial deterioration of startability of the engine. This is considered to be caused by the following factors:
(1) Once the fuel pump for supplying fuel to the diaphragm chamber has become empty, sealing performance of a suction valve and a discharge valve in the fuel pump is reduced, so that it takes a rather long time to restart fuel supply. PA1 (2) If the diaphragm chamber is filled with air, it takes a long time to expel the air out of the diaphragm chamber. PA1 (3) Introduction of air within the pipe connecting between the diaphragm chamber and the fuel pump into the diaphragm chamber increases the effect of the factor as described in the above paragraph (2).
In order to solve the problem, several techniques have been developed. For example, Japanese Laid-Open Utility Model Publication No. 51-43315 discloses a technique in which a manual pump is provided in a pipe connecting between the fuel tank and the carburetor, the manual pump being operated before starting of the engine to supply fuel to the carburetor, with a tickler lever operated at the same time to open a fuel valve in the inlet of the diaphragm chamber and an overflow valve. Japanese Laid-Open Patent Publication No. 55-69748 or U.S. Pat. No. 4,271,093 discloses another technique in which the diaphragm chamber may be connected with a manual suction pump, which is operated before starting of the engine to suck fuel within the fuel tank into the diaphragm chamber.
In the former prior art technique, both of the manual pump and the tickler lever must be operated before starting of the engine, and consequently both hands of a user are engaged for them, resulting in cumbersome handling.
In the latter prior art technique, the manual pump must be also operated before starting, requiring in cumbersome handling.